Cannot start Celery Worker (Kombu.asynchronous.timer)

I had this issue with the default Celery installation from pip (3.1.26Post2). As mentionned above, I installed instead version 3.1.25, but Celery was still not working. Thus I explicitly installed the latest version:

pip install Celery==4.3

and everything is working now!

I landed here after I tried to install django-celery while reading celery 4.4 documentation, this package forces celery version to 3.1.26.post2, so I had to:

pip uninstall django-celery
pip uninstall celery && pip install celery # Uninstall 3.1 and install latest

As documentation clearly says:

Django is supported out of the box now so this document only contains a basic way to integrate Celery and Django. You’ll use the same API as non-Django users so you’re recommended to read the First Steps with Celery tutorial first and come back to this tutorial.

I have the same problem, but solved it when reinstall celery with version 3.1.25

pip uninstall celery && pip install celery==3.1.25

Maybe because windows is not officially supported by celery 4， https://github.com/celery/celery/issues/3551

TL;DR: remove the kombu directory from the root of your virtualenv (if it exists). It may only fail on Windows.

It seems to be a quirk. I found the same error and I checked out what was happening.

The wheel package that pip downloads looks fine (kombu.asynchronous.timer exists in it). The release for the last version (currently 4.2.0) also is fine. What was strange is what I found in my virtualenv installation.

I found a kombu directory at my virtualenv root which has the content of the library but it also has an "async" directory, alongside an "asynchronous" one. These directories aren't from the 4.2.0 release, as async has the timer.py file but asynchronous doesn't.

From where did it come? It appears that from the wheel's data directory.

So, the solution: I removed the kombu directory from the root of my virtualenv and celery worked.